In this project we hope to learn something of the mechanism by which genetic information is repressed and derepressed, by studying the amounts, structures, and rates of synthesis of chromosomal materials, in particular the histones, and tubulin. The study will be carried out on material derived from tissues which are in different phases of genetic expression, more specifically in mammary cell cultures exposed to different hormonal treatment (insulin, prolactin, cortisol). BIBLIOGRAPHIC REFERENCES: Wiche, G., and Cole, R. D., Reversible in Vitro Polymerization of Tubulin from a Cultured Cell Line (Rat Glial Cell Clone C6). Proc. Nat'l Acad. Sci. U.S. 73, 1227-1231 (1976). Wiche, G., Lundblatt, V., and Cole, R. D., Competence of Soluble Cell Extracts as Microtubule Assembly Systems: Comparison of Simian Virus 40 Transformed and Nontransformed Mouse 3T3 Fibroblasts. J. Biol. Chem. 252, 794-796 (1977).